Java ComboBox - 打印出所选项目
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ComboBox - printing out the selected item
提问by tom
I am a little stuck. I can't figure out a much bigger problem than this, so I am going to the roots to eventually build my way up!
我有点卡住了。我想不出比这更大的问题，所以我要从根源开始，最终建立自己的道路！
I can't print the selected item in the combo box, currently I have an ActionListenerfor it:
我无法在组合框中打印所选项目，目前我有一个ActionListener：
box.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent evt) {
myBox(evt);
}
});
...
protected void myBox(ActionEvent evt)
{
if(myBoxName.getSelectedItem().toString() != null)
System.out.println(myBoxName.getSelectedItem().toString());
}
I would expect this to print out to the console every time I change the selected item, but it doesn't. This should be so easy though!
我希望每次更改所选项目时都会将其打印到控制台，但事实并非如此。不过，这应该很容易！
Thanks
谢谢
采纳答案by Peter Lang
I just tried your code and it works fine. Whenever I change selection, the selected text is written to System.out.
我刚刚试过你的代码，它工作正常。每当我更改选择时，选定的文本都会写入System.out.
The only thing I changed was the check for myBoxName.getSelectedItem().toString() != null, I check for myBoxName.getSelectedItem() != nullinstead. This should not be related to your problems though.
我唯一改变的是检查myBoxName.getSelectedItem().toString() != null，我myBoxName.getSelectedItem() != null改为检查。不过，这不应该与您的问题有关。
public class ComboBoxTest {
private JComboBox comboBox = new JComboBox(
new DefaultComboBoxModel(new String[] { "Test1", "Test2", "Test3" }));
public ComboBoxTest() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.setSize(200, 100);
comboBox.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent evt) {
myBox(evt);
}
});
frame.getContentPane().add(comboBox);
frame.setVisible(true);
}
protected void myBox(ActionEvent evt) {
if (comboBox.getSelectedItem() != null) {
System.out.println(comboBox.getSelectedItem().toString());
}
}
}
